The disposal of organic solid waste has become an increasingly severe problem in view of the increasing population, the concentration of populations in urban and suburban areas and the increasing number of industries generating organic solid wastes. Some national jurisdictions are about to enter a zero landfill era, which necessitates the immediate solution to waste and in particular solid waste disposal.
A large fraction of such organic waste is combustible and is made up of such material as paper, textiles, leather, rubber, yard wastes, wood, wood wastes and bark, garbage, plastics, paints, industrial wastes and sludges and sanitary sewage treatment products. The process of this invention is directed to the conversion of the entire spectrum of wastes into products which can be used as a fuel or fuel supplement.
Inasmuch as it is becoming increasingly difficult to dispose of wastes, particularly solid waste by such previously used means as dumping and filling, a critical need has arisen to find other techniques for waste disposal, such techniques of necessity being those which do not create pollution problems and of preference those which do not require the expenditure of appreciable amounts of energy. Moreover, if the end product or products of the disposal process are themselves usable, the process is even more desirable.
In general, the processes more recently proposed for solid waste disposal may be classed as bulk reduction, conversion or reclamation. Although some advances in bulk reduction (densification) have been made, each of the techniques used (baling, incineration, etc.) have inherent drawbacks including disposal of the densified material, pollution control and the like. The techniques used include pyrolysis (destructive distillation or decomposition at elevated temperatures, e.g., 750°-1600° F., in the absence of air or other reactive or oxidizing gases), composting (aerobic conversion of cellulose waste into inert humus-like material by aerobic bacteria), hydrogenation, wet oxidation, hydrolysis, anaerobic digestion, biological fractionation and the like.
Recycling involves the separating out from the solid waste of such materials as glass, plastics, metals, papers, textiles and the like for reuse in one form or another. However, other than some forms of papers, plastics and textiles, the combustible component of organic solid wastes which has caloric value has not been recovered. Only recently has any serious attempt been made to convert the combustible materials to a form in which they could be used as a fuel.
Older processes such as those in U.S. Pat. Nos. 3,961,961 and 4,008,053 used acid treatment to embrittle organic waste material for grinding to produce solid fuels. More recently the processes are used to produce liquid flowable fuels as in U.S. Pat. Nos. 6,000,639 and 6,202,577.
It is a primary advantage of this invention that it is possible to treat all waste including municipal and industrial solid wastes and liquid wastes to form a consistent liquid flowable fuel or fuel supplement using a relatively small amount of energy and employing known system components. The resulting product material is usable as a fuel or fuel supplement in existing combustion equipment without requiring any substantial modification. This product retains essentially all of the caloric content of the original waste material from which it is formed. It is another advantage that the process described can be carried out with the expenditure of relatively little energy so that the net result of the process is an energy gain in the form of caloric fuel.
Still another advantage of this invention is that the process does not involve substantial pyrolysis, decomposition or chemical conversion and therefore does not generate pollution control problems. It is a further advantage of this invention that the process described can be carried out in available system components and which can be readily adapted to conditions prevailing within a given area to form a fuel product best suited for the area in which it is produced or to be used. It is yet another primary advantage of this invention that a unique fuel or fuel supplement is produced. It is yet another advantage that such a fuel or fuel supplement may be stored and handled without under going decomposition.
Other advantages of the invention will be apparent hereinafter.